1. Field of the Invention
The present invention relates to printing performed using an ink-jet printer, and more particularly, to a method and apparatus for aligning an image of an ink-jet printer having a high quality to be printed on a printing paper.
2. Description of the Related Art
A fire pulse needed in a conventional apparatus for aligning an image of an ink-jet printer is generated using elements. As shown in FIG. 1, such a conventional apparatus includes, for example, an encoder sensing unit 10, a reference clock generating unit 12, a moving speed detecting unit 14, an interrupt generating unit 16, a central processing unit (CPU) 18, and a fire pulse generating unit 20. The fire pulse is a signal used to designate a printing position of an image to be printed on a printing paper. The encoder sensing unit 10 generates an encoder signal by sensing an encoder strip when a carriage (not shown) moves and outputs the generated encoder signal to the moving speed detecting unit 14 and the interrupt generating unit 16. The reference clock generating unit 12 generates a reference clock signal having a specified cycle and outputs the generated reference clock signal to the moving speed detecting unit 14. The moving speed detecting unit 14 detects the moving speed of the carriage in response to the encoder signal input from the encoder sensing unit 10 and the reference clock signal input from the reference clock generating unit 12 and outputs the detected moving speed to the CPU 18. In other words, the moving speed detecting unit 14 obtains the moving speed of the carriage by counting the cycle of the reference clock signal corresponding to the encoder signal having one cycle. The interrupt generating unit 16 generates an interrupt at each cycle of the encoder signal input from the encoder sensing unit 10 and outputs the generated interrupt to the CPU 18. The interrupt is a signal periodically generated by the interrupt generating unit 16 so that the CPU 18 forcibly controls calculation of a delay time of a fire pulse while a program is executed. The CPU 18 calculates the delay time of the fire pulse using the moving speed of the carriage input from the moving speed detecting unit 14 whenever the interrupt is generated by the interrupt generating unit 16, and outputs the calculated delay time of the fire pulse to the fire pulse generating unit 20. The fire pulse generating unit 20 generates the fire pulse after the delay time of the fire pulse input from the CPU 18 passes and outputs the generated fire pulse through an output terminal OUT1.
FIGS. 2A through 2C illustrate signals output from the encoder sensing unit 10, the reference clock generating unit 12, and the interrupt generating unit 16 shown in FIG. 1. FIG. 2A illustrates an encoder signal sensed by the encoder sensing unit 10, FIG. 2B illustrates a reference clock signal generated by the reference clock generating unit 12, and FIG. 2C illustrates an interrupt generated by the interrupt generating unit 16 at each cycle of the encoder signal. As shown in FIGS. 2A through 2C, the cycle of a reference clock signal corresponding to the encoder signal having one cycle is 6 times, and the moving speed of the carriage can be obtained by multiplying the cycle of the reference clock signal by a time occurring at one cycle of a specified reference clock signal.
However, when a single-pass printing operation is performed, a printing material having a low resolution is inevitably obtained, and in an acceleration and deceleration section of the carriage, the delay time of the fire pulse due to a variation in speed should be obtained by generating an interrupt at each cycle of an encoder signal. In other words, when an encoder interrupt is generated, the current moving speed of the carriage is sensed, and the delay time for the fire pulse for compensating an expected shooting position error is detected by predicting a shooting position of a printing paper from a sensing result. Frequent generation of an interrupt causes lowering of a printing processing speed of a printer. In addition, when a multi-pass printing operation is performed so as to increase resolution, the printing operation is performed only in a constant speed section of the carriage, or even though the printing operation is performed in the acceleration and deceleration section of the carriage, due to a fixed delay time for a fire pulse, a printing material having a low resolution is inevitably obtained.